Of interest to digital photographers with flash memory

On Sat, 11 Aug 2012 16:31:09 +0100, "R. Mark Clayton"
wrote:


wrote in message
.. .
On Thu, 09 Aug 2012 21:11:25 -0500, Rich wrote:

wrote in
:


While looking around in a drawer, I discovered a small flash memory
card I bought in 2000, it's a 16m card. Yes, that's meg, not gig!

Anyway, there are still photos on it, and I can read it with no
problems.

12 years so far, not bad!

I'm going to hide it away and check in a few years, if I last that
long!



Probably a better idea than DVD's, cloud storage, etc. Expensive though
if you were to use it for all images. Also, I'm not sure about the
longevity of solid-state hard drives either.

As far as I know these memories depend on glass insulation to keep the
charge
alive or something like that... there are 2 possible problems here, 1 is
radiation affecting the charge directly or just natural decay through
other
resistive paths, or 2 something that activates the write mode by mistake
E.G.
something biasing it to the "on" state. Anything that can be written to
can be
written in error.

Unfortunately I haven't kept up with this technology...


IIRC

Flash and EPROMS rely on floating gate. Typically electrons are pumped into
(or out of) an insulated region using a higher voltage than needed to read
the device.

In the case of EPROMs erasure was achieved by exposure to short wavelength
UV light. Absorbed photons raised the potential of electrons in the atom
concerned above the potential need to escape the floating gate quantum
mechanically. In the case of Flash (or one time EPROMs in plastic packages)
and electromagnetic radiation that can penetrate the case (X-ray, gamma rays
etc.) can gradually erase the memory.


I remember spending hours and hours erasing Eproms and re-programming them... I
think the biggest we had was 512k... it usually took about 8 chips to get
something to do something useful!

On 2012-08-12 20:24 , wrote:

I remember spending hours and hours erasing Eproms and re-programming them... I
think the biggest we had was 512k... it usually took about 8 chips to get
something to do something useful!


512K?

We used something like 28 chips to do 28 k words (EPROMs and PROMS).
The EPROM's had to sit for an hour under UV lights to erase them.

--
"Civilization is the limitless multiplication of unnecessary necessities."
-Samuel Clemens.

wrote in message
...

I remember spending hours and hours erasing Eproms and re-programming
them... I
think the biggest we had was 512k... it usually took about 8 chips to get
something to do something useful!


The first commercially available EPROMs were the 1702 (512x4 bits).
The first I used were the 2708 (1kx8 bits). These were a PITA with three
supply rails and an age to erase.
These were in ceramic DIP's with a quartz window. You had to cover the
window to prevent accidental erasure by sunlight (~fortnight) or flourescent
lights (about three years).

After a slow start EPROMs followed Moore's law, with capacity and the number
of pins gradually increasing over the years and the cost per bit falling.
Programming became easier too. The last I used were 27C256.

The last generally available EPROMs were there 27C080 (1Mx8 bits), although
there were specialist chips up to as much as 4Mb. There were also some
embedded processors that incorporated EPROM and could be reprogrammed in the
field (but not normally in situ, although some times first programming could
be done on the board, however erasure required removal).

Other persistent memory technologies included battery backed static RAM and
electrically alterable or erasable ROM (EAROM & EEPROM), but the former
forget when the battery runs down and the latter did not show the same
capacity growth.

In the end [nand] flash emerged as the dominant technology, for a while
exceeding Moore's law - you can now get 32Gb on a micro SD. So 1971 2048
bits ; now 274,877,906,944 bits. Price 1kb in mid 1970's ~$30, 32Gb now
~$20.

On 2012-08-11 11:25 , R. Mark Clayton wrote:
"Alan Browne" wrote in message
...
On 2012-08-10 13:00 , R. Mark Clayton wrote:
"Rich" wrote in message
...
wrote in
:


While looking around in a drawer, I discovered a small flash memory
card I bought in 2000, it's a 16m card. Yes, that's meg, not gig!

Anyway, there are still photos on it, and I can read it with no
problems.
SNIP

1. Chemically, physically and electrically stable media.

Quite poor actually. When subject to light and heat (and possibly
humidity) the information decays rapidly. Such CD's need to be kept in
cool, dark, dry places to last a long time.

Well [obviously] yes. I wasn't suggesting hanging them up in the garden to
scare cats.

Not the point. Many people have them lying around their living room
where there is ample light and uncontrolled humidty. When hit by the
sun they also heat up.

Much the same applies to other media such as film or prints. etc.

To be sure. Or use "gold" DVD media. Lasts about 100x longer (and also
needs to be kept in cool, dry, dark storage.


If you mean commercially 'pressed' CD-ROMs, that is another matter as the
information carrying layer is not an organic dye as it is for the one-ime
writeable CD's we use for storage.

True, but the change is pretty irreversible. Similarly one won't get
spontaneous change.


OTOH, there are better versions such as the "gold" archival CD/DVD's that
will last much longer.

Glad to hear it - use those if you can afford gold.

For the data that matters, it's not at all that expensive. Be choosy
(about the data).


--
"C'mon boys, you're not laying pipe!".
-John Keating.

On Sun, 12 Aug 2012 20:33:14 -0400, Alan Browne
wrote:

On 2012-08-12 20:24 , wrote:

I remember spending hours and hours erasing Eproms and re-programming them... I
think the biggest we had was 512k... it usually took about 8 chips to get
something to do something useful!


512K?

Yes, but that's bits, not bytes! I forget the part number now but it had 512 in
it... so it was a 64k byte chip... some part # like 27c512a or something...

The machines (hot bearing detectors) had 2 of these chips on the Z80 processor
board (along with PROMS), and 8 or more on the voice generator board. It "spoke"
its warning message over the radio, the words were in the Eproms as wav chunks.
We had special ones being in Quebec... "BOITE CHAUD - NORD RAIL!"

We used something like 28 chips to do 28 k words (EPROMs and PROMS).
The EPROM's had to sit for an hour under UV lights to erase them.

I often wondered how long those lamps would last, ours was going 8 hours a day!

I think one thing that led to the demise of those chips was the countless
variations and non-standards... our last programmer was a computer system with
hundreds and hundreds of different chips in the database. You didn't see the "c"
on the end of the part number? Too bad - it's now toast!

On Mon, 13 Aug 2012 12:30:28 +0100, "R. Mark Clayton"
wrote:


wrote in message
.. .

I remember spending hours and hours erasing Eproms and re-programming
them... I
think the biggest we had was 512k... it usually took about 8 chips to get
something to do something useful!


The first commercially available EPROMs were the 1702 (512x4 bits).
The first I used were the 2708 (1kx8 bits). These were a PITA with three
supply rails and an age to erase.
These were in ceramic DIP's with a quartz window. You had to cover the
window to prevent accidental erasure by sunlight (~fortnight) or flourescent
lights (about three years).

After a slow start EPROMs followed Moore's law, with capacity and the number
of pins gradually increasing over the years and the cost per bit falling.
Programming became easier too. The last I used were 27C256.

The last generally available EPROMs were there 27C080 (1Mx8 bits), although
there were specialist chips up to as much as 4Mb. There were also some
embedded processors that incorporated EPROM and could be reprogrammed in the
field (but not normally in situ, although some times first programming could
be done on the board, however erasure required removal).

Other persistent memory technologies included battery backed static RAM and
electrically alterable or erasable ROM (EAROM & EEPROM), but the former
forget when the battery runs down and the latter did not show the same
capacity growth.

In the end [nand] flash emerged as the dominant technology, for a while
exceeding Moore's law - you can now get 32Gb on a micro SD. So 1971 2048
bits ; now 274,877,906,944 bits. Price 1kb in mid 1970's ~$30, 32Gb now
~$20.


I remember those battery proms, Dallas chips I think they were...

The last system I used before I retired had a few empty sockets on the board.
You brought a set of new updated software programming chips, installed them onto
the board, set a jumper, re-installed the board, powered up and down, took it
out, removed the jumper and chips, and presto! All new programming!

No idea how it actually worked, I was just following a direction sheet!

wrote in message
...
On Sun, 12 Aug 2012 20:33:14 -0400, Alan Browne
wrote:

On 2012-08-12 20:24 , wrote:

I remember spending hours and hours erasing Eproms and re-programming
them... I
think the biggest we had was 512k... it usually took about 8 chips to
get
something to do something useful!


512K?

Yes, but that's bits, not bytes! I forget the part number now but it had
512 in
it... so it was a 64k byte chip... some part # like 27c512a or
something...

The machines (hot bearing detectors) had 2 of these chips on the Z80
processor
board (along with PROMS), and 8 or more on the voice generator board. It
"spoke"
its warning message over the radio, the words were in the Eproms as wav
chunks.
We had special ones being in Quebec... "BOITE CHAUD - NORD RAIL!"

We used something like 28 chips to do 28 k words (EPROMs and PROMS).
The EPROM's had to sit for an hour under UV lights to erase them.

I often wondered how long those lamps would last, ours was going 8 hours a
day!

They were just flourescents without the phosphor - last for years.


I think one thing that led to the demise of those chips was the countless
variations and non-standards... our last programmer was a computer system
with
hundreds and hundreds of different chips in the database. You didn't see
the "c"
on the end of the part number? Too bad - it's now toast!

Early ones were easily fried. Later ones tended to have standard
programming voltages etc., although I do remember one engineer getting a
brief white flash out of the the little quartz window, which afterwards was
quite a good mirror. Not as bright as a neon straight across the mains,
which I managed in my early teens...

On Thu, 16 Aug 2012 21:30:12 +0100, "R. Mark Clayton"
wrote:


I often wondered how long those lamps would last, ours was going 8 hours a
day!

They were just flourescents without the phosphor - last for years.


I think one thing that led to the demise of those chips was the countless
variations and non-standards... our last programmer was a computer system
with
hundreds and hundreds of different chips in the database. You didn't see
the "c"
on the end of the part number? Too bad - it's now toast!

Early ones were easily fried. Later ones tended to have standard
programming voltages etc., although I do remember one engineer getting a
brief white flash out of the the little quartz window, which afterwards was
quite a good mirror. Not as bright as a neon straight across the mains,
which I managed in my early teens...



I once had a large solenoid coil I used as a ballast for a 50 watt green
fluorescent. You could vary the brightness by adjusting the position of the
plunger! It could go VERY bright indeed!